linux-kernel - Re: [PATCH v6 07/10] hda: cs35l41: Add support for CS35L41 in HDA systems

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Date:   Mon, 31 Oct 2022 16:34:14 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Lucas Tanure <tanureal@...nsource.cirrus.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Mark Brown <broonie@...nel.org>, Takashi Iwai <tiwai@...e.com>,
        ALSA Development Mailing List <alsa-devel@...a-project.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        patches@...nsource.cirrus.com,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 07/10] hda: cs35l41: Add support for CS35L41 in HDA systems

On Mon, Oct 31, 2022 at 7:38 AM Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
> On Thu, Jan 06, 2022 at 02:29:58PM +0200, Andy Shevchenko wrote:
> > On Fri, Dec 17, 2021 at 5:45 PM Lucas Tanure
> > <tanureal@...nsource.cirrus.com> wrote:

...

> > > +       cs35l41->reset_gpio = fwnode_gpiod_get_index(&adev->fwnode, "reset", cs35l41->index,
> >
> > Please, do not dereference fwnode pointers.
> > Also, why can't you use the device instead of fwnode?
>
> We are doing "acpi_dev_put(adev);" a few lines above, so using adev in
> the call to fwnode_gpiod_get_index() is technically use-after-free,
> isn't it?

Right, but I believe this is in response to the author and not to me.

> Also, why can't we do
>
>         cs35l41->reset_gpio = gpiod_get_index(acpi_dev, "reset",
>                                               cs35l41->index,
>                                               GPIOD_OUT_LOW);
>
> since acpi_dev is device structure corresponding to adev and we are
> getting the rest of the properties from it?

I remembered that I have also stumbled over that, but IIRC the point
here is that ACPI tables might be broken (since the multi-instance
device is a gray area to begin with). So we need clarification from
Cirrus to understand what the cases they want to cover with this
twisted code to get a GPIO.

> I saw downthread that there was supposed to be a patch addressing
> several issues raised by Andy, was it ever submitted?

-- 
With Best Regards,
Andy Shevchenko